i didn't mean lower like 3k RPMs, I meant lower like 1K short of redline, so that if the shift is slow then he's not gonna hit fuel cutoff during the shift. And 1-2 is faster than 2-3 for me for some reason...don't know why.

 

As I understand the term, it refers to a clutching method when speedshifting. I beleive "blipping" the clutch is a stabbing like motion with your foot, as opposed to "sidestepping" which is a down and left motion. While on the subject, let's do speedshifting 101 as it was taught to me;

Disclaimer: This is how it was taught to me by a non-professional, but it works for me. All information (with the possible exception of the use of the term "blipping") is accurate to the best of my humble knowledge. Price and participation may vary, see store for details.

First of all, we need to understand that speed shifting is purely a competition oriented technique. As with anytime we push machines to their limits (which is what competition is all about), a certain amount of risk must be assumed. (don't run w/scissors, you're gonna poke an eye out, you'll fall and break your neck, etc, etc....)

That being said, there are four things that need to take place when you shift a car. They need to blend together into one smooth action, but to understand them, we need to break them down individually. In order of occurance they are;

1) Pulling the trans. out of gear
2) Pushing the clutch in enough to get into the next gear
3) Putting the trans. into the next gear
4) letting out the clutch

We will look at these in further detail in a moment.

Throttle:

The only real benifit of WOT (wide open throttle) shifts is with the stage1 or better PCM. Without a stage kit, the PCM will cut boost when the clutch is pushed in. The benifit of WOT shifting with a stage kit is that the turbo stays "spooled", so you enter the next gear under full boost. This being said, WOT shifting is the riskiest. It's easier to miss a gear, and the extra power increases the likelyhood of damage if you do. For this reason, most people WOTS from 1st to 2nd, and from 3rd to 4th (if they're not at the end of the qtr mi by then), but will come off the gas for the more difficult 2nd to 3rd shift. It's a matter of how confident you are of doing it successfully.

The Breakdown:

1) Pulling the trans. out of gear. This is where it starts. The clutch pedal doesn't have to be in to pull the car out of gear, but it better be in enough by the time you enter the next gear. Contrary to "normal" shifting (push in clutch, shift, let out clutch), a speedshift starts by beginning to pull the car out of gear.

2) Pushing in the clutch. Just before the shifter is entering neutral is when this motion wants to begin. The idea is to have the pedal reach the point of disengagement just as the shifter is entering the next gear. Keep in mind that no matter how fast you can move, each of these moves has some lag (reaction time) and some duration (the time it takes to complete the movement). That is why this "series of events" approach is important.

3) Putting the trans. into the next gear: This motion is already taking place. The importance of breaking it out is to realize that even though it is the same motion that began at step 1, entering the next gear is when the clutch pedal needs to be down to the point of disengagement. Not until after pulling out of gear and then passing neutral. Also note that while the shift motion must be firm, It isn't necessary to brutally slam the shifter into gear either.

4) Letting out the clutch. If you've done everything right so far, we are at the millisecond in time where the trans. is in the next gear and the clutch pedal is just far enough down to disengage. It is also time to pick an option (well not really. If you didn't pick an option before you began the shift then you're pretty much screwed at this point. The time it would take your mind to compute a decision would definitely put you deep into redline). Blip or sidestep. If you want to win the race and have no concern about beating on your clutch pedal, then sidestep may be for you. If you are slightly more conservative (and well practiced) then you might be a "blipper". Here are the nuances of both.

Blipping is easier on the clutch pedal, but usually takes a little more practice to do quickly. It's also a matter of the person who's doing it and their own preference. Here again, understanding the minutia is important.

With blipping, you push in the clutch just far enough for the shifter to go into the next gear, and then pick your foot up. Your foot has to change direction with this method, so the lift up movement almost needs to start at the same time as the push down motion. This may sound strange, but if you try to do it as fast as you can you'll see what I mean. Because of the direction reversal, completing the motion of the blip usually takes a little longer than the sidestep. Most agree though that if you start the motion just as you're coming out of gear, the end result can be just as good.

Sidestepping is a down and to the left motion that causes your foot to "slip off" the clutch pedal just as it reaches the point of disengagement. As you can imagine, this causes the pedal to slam back up. Not as pretty as the blip, but because it's a one way motion it sure can be quick. Because of this you will want to begin this motion a little later than the blip. About the time the shifter reaches nuetral. Also, be careful not to get an ankle gouge from the returning pedal (ouch!).

With these or any other techniques, always practice slowly at first with the car off (and E-brake on). Once you think you're getting the hang of it, try some low rpm quickshifts, letting off the gas while shifting. Next try holding about 2k RPMs while shifting. Here you will be able to tell how well you're doing by the rise in RPM (it should be minimal) and there will be a distinct absense of any grinding sound. [:@]
When and if you think you've got it nailed, and only then, go for the glory! Remember though that keeping the turbo pumping it's little iconel steel *** off is the whole point, so you have to shift before redline. How much before depends on how fast you can shift. If you hit the rev limiter, the turbo kicks out and it's all for not.

Hope this helps

Scott

Edit note: when I started this reply, there were only 2 responses. Took me forever to type. Sorry if it's redundant

 

WOW!!! Great job on the shifting 101. I'm going to print this out.

 

I did my first few WOT shift this weekend. I just installed my S2 with exhaust and BOV and I was trying to get the hang of it. I just about broke my face when I finally got it. I couldn't stop smiling all day! My cheeks still hurt.[sm=grinangel.gif]

 

I have to get this off my chest. I did not notice any "boost hold" feature in my stage 1. Hell, it held boost on WOT shifts before I had the computer. The only thing I noticed right away was part throttle boost was enhanced, plus a couple of ticks of the 1320. After the manual boost controller was added, then it kicked butt!

From the turbo cars I have owned over the years blipping the throttle during shifts always kept the turbo spinning.

Someone enlighten me.

 

Interesting point, but there may be an important distinction. From what LSP tells me, you're driving abilities are much better than average. I am new to turbos, but I have been wondering how important the boost hold feature is to a person who speedshifts well. This is where my lack of turbo experience may show, but how much boost could be lost in the somewhere-south-of-a-1/10-of-a-second time frame that the clutch is actually in? I don't know how the PCM actually goes about cutting the boost, but unless there's disc brakes on one of the impellers, then there seems to be only a couple of practical / efficient options. Openning the BOV seems like it would be the most instant cut, meaning the still spinning turbo would only need to re-charge the pipe. The only other possibility I can imagine would have to do with the wastegate. Can someone explain the specifics of the wastegate's function to me (and maybe others) and how it works? If it directs exhaust flow over the turbine (and the PCM redirects/closes the wastegate) then I would think that the turbo would still "freewheel" during this brief lapse. I suppose that all of this assumes that the PCM returns all things to normal the instant that the clutch is back out, and doesn't have a timeout delay. While I'm at it (showing my lack of turbo knowledge that is), I have another question. My understanding is that there are two impellers. One in (or just off of) the exhaust manifold to drive the other impeller in the intake stream. Are the two connected directly (common shaft), 1:1, or are they gear / belt & pulley / clutch driven? If clutched, I suppose this would give another possibility of how the PCM cuts boost. Any info would be appreciated. Wow, my brain hurts....

Scott

 

Holy Cow Wht Lightn!!!!!

Yeah, the turbo has two impellers, one is driven by exhaust gas which drives the other side to compress the intake charge. I agree with you about the loss of boost when a shift only takes a tenth or so. I think your correct about the BOV....if it did not open, the charge pressure in the piping and intercooler would stall the compressor. Disconnect the BOV vacuum line and you'll hear it loud and clear.

The only thing I can think of is they are playing with the wastegate solenoid, bleeding off pressure to the wastegate actuator??????

Now my brain hurts man!!! LOL

I'm on a mission now....."How do they control the boost hold feature, or what actuates it"?[sm=dontgetit.gif]

 

Can anyone else chime in on the "how does the PCM cut boost" question above, it's teasing my brain.
(and yes, it must have very good aim!) }:-)~

Scott

 

What I've have noticed on a few of my Turbo cars is the ECU and easly pull timing out, and that has the effect of lowering the boost almost right away.

 

I GOT THE SCOOP.

The boost hold feature is only activated in a WOT shift. Which means......drumroll.......anytime the PCM see's the TPS voltage 2.50 volts above the mininum TPS voltage, it will go into WOT boost hold.

Example: Say your minimum TPS voltage is .79 volts, .79+2.50=3.29 volts. When 3.29 volts is seen, is goes open loop WOT mode. SO, you dont have to necessarly
have to have it to the rug. Ths 3.29 volts is actually obtained at 75% throttle or more.

Here is the interesting part, if you cycle the key without starting the car, every time you do this it raises minimum TPS by .02 volts, UNTIL you shut it off and restart the car. I heard of some people cycling the key to reset the PCM. So it is possible that if you cycle the key enough, minimum TPS will be so high, the PCM will never see WOT. Minimum TPS is generally not the same from car to car, but only varies a few tenths.

My conclusion......Any time you shift at 75% throttle or more WITHOUT lifting off the gas, the boost hold will operate. Jeez, I could have saved alot of writing just with that last statement, LOL.

Edit....funny. The engineer I talked to said he would not recomend doing this until the car is out of warranty, LMAO.